EFFECT OF NON-ALCOHOLIC FATTY LIVER DISEASE (NAFLD) ON HEPATIC DRUG METABOLISM ENZYMES IN HUMAN

Significant changes in dietary habits have led to a rampant increase in metabolic disorders. Non-alcoholic fatty liver disease (NAFLD) is one such disorder characterized by the excess buildup of fat in hepatocytes of people who drink little or no alcohol. If not managed, NAFL (simple steatosis) progress into nonalcoholic steatohepatitis (NASH) and further deteriorate to cirrhosis leading to severe illness or even death. Drug disposition proteins (enzymes and transporters) in liver control the systemic exposure of drugs and xenobiotics in human and drive the efficacy as well as adverse events in the body. Therefore, it is critical to address the effect of NAFLD on the abundance of these proteins. A variation would result in an altered pharmacokinetic and/or pharmacodynamic profile of substrate drugs in patients with NAFLD. Most studies were performed in preclinical species (rat, mice) and only a few reports are available in human. The primary objective of this doctoral project was to investigate the effect of NALFD on the abundance of hepatic drug disposition proteins (DDP) in a human liver-bank. The levels of proteins were determined using an LC-MS/MS based label-free, global proteomics method. In addition, CYP3A4 enzyme kinetics parameters were determined using midazolam as a probe substrate. Considerable changes in the protein expression and activity of CYP3A4 and CYP1A2 were found in NAFL and NASH. Only marginal alterations were observed for other cytochrome P450 enzymes in this study. Levels of uridine 5\u27-diphospho-glucuronosyltransferases (UGT) and sulfotransferases (SULT) in NAFLD were mostly unaltered. Dysregulation of mitochondrial proteins involved in lipid metabolism (ACADSB, ACSM3/5, CPS1) was also observed. A significant downregulation of CYP3A4 protein and activity but not mRNA in NAFLD was observed suggesting that post- transcriptional changes may play a more significant role in the observed phenotypic perturbations for the isoform. Overall, enzyme kinetics and quantitative protein abundance data from this project will be important in the development of physiologically based pharmacokinetic (PBPK) models for prediction of drug disposition in the NAFLD population